/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import java.io.Serializable;
import java.util.List;
import javax.annotation.Nullable;

/**
 * An ordering that treats all references as equals, even nulls.
 *
 * @author Emily Soldal
 */
@GwtCompatible(serializable = true)
final class AllEqualOrdering extends Ordering<Object> implements Serializable {
    static final AllEqualOrdering INSTANCE = new AllEqualOrdering();

    @Override
    public int compare(@Nullable Object left, @Nullable Object right) {
        return 0;
    }

    @Override
    public <E> List<E> sortedCopy(Iterable<E> iterable) {
        return Lists.newArrayList(iterable);
    }

    @Override
    public <E> ImmutableList<E> immutableSortedCopy(Iterable<E> iterable) {
        return ImmutableList.copyOf(iterable);
    }

    @SuppressWarnings("unchecked")
    @Override
    public <S> Ordering<S> reverse() {
        return (Ordering<S>) this;
    }

    private Object readResolve() {
        return INSTANCE;
    }

    @Override
    public String toString() {
        return "Ordering.allEqual()";
    }

    private static final long serialVersionUID = 0;
}
